1. Field of the Invention
The invention relates to a flame-retardant polyamide molding material for sheathing optical waveguides and optical cables, and the use thereof.
2. Discussion of Background Information
Mostly glass fibers (glass optical fibers, GOF) are used as optical fibers, using which large quantities of data may be transmitted over large distances. Plastic optical waveguides (polymer optical fibers, POF) can also be used for transmitting light signals over short distances. The optical fibers are coated directly at the fiber producer for better handling and for protection, optionally with a lacquer and in any case with a first plastic layer, the so-called primary coating, also called cladding. In the case of polymer optical fibers, the primary coating consists of a fluoropolymer, for example.
The optical fiber provided with a primary coating is designated in this application as an optical waveguide.
The secondary coating or sheathing or enveloping of the optical waveguide with plastic is performed during the core production. In general, the term sheathing is primarily used as the generic term for the secondary coating or sheathing or enveloping of an optical waveguide or in the case of an optical cable hereafter in the description of the invention.
The manner of designing such sheaths in the case of optical waveguides or optical cables is known to a person skilled in the art. A representative and recognized standard work for this purpose is the “Kabelhandbuch [Cable Handbook] Daetwyler” from October 2000 (Daetwyler Kabel+Systeme GmbH, D-85375 Neufahrn), which can be retrieved directly via the Internet as a UNILAN handbook from Fachhochschule Flensburg [Flensburg Polytechnic] (Germany) under the address: http://www2.wi.fh-flensburg.de/wi/riggert/Netzwerke/Kabelhandbuch-Daetwyler.
The construction of glass fiber cables is described in Chapter 4.6 of the Kabeihandbuchs-Daetwyler. According to subchapter 4.6.2 about core types, the unit made of optical fiber, primary coating, and secondary coating is designated as a core, i.e., this unit forms an optical core. According to this subchapter, there are fundamentally two embodiments for the secondary coating or sheathing, specifically a tight envelope (tight core or full core) or a loose envelope (hollow core), cf. FIG. 4.28. If a plurality of optical waveguides are inserted into a loose envelope, such a unit is referred to as a bundle core, cf. FIG. 4.30. An intermediate step between a full acore and a hollow core is the compact core according to FIG. 4.32, in which the sheathing has only a small distance from the optical fiber. Intermediate spaces between optical waveguide and sheathing are filled out using a gel.
An optical cable is obtained according to subchapters 4.6.3 and 4.6.4 by twisting together a plurality of optical cores to form a cable core, and applying a suitable jacket around the cable core, cf. FIG. 4.34. This jacket of an optical cable which sheaths everything is also understood as sheathing as defined in the present invention.
Transparent copolyamides are described in DE 37 17 928 A1, which necessarily contain bis(4-amino-3-methyl-5-ethyl-cyclohexyl)methane. Their suitability for optical waveguide sheathing is mentioned. Inter alia, flame retardants are mentioned as possible additives, without being specified in greater detail.
Polyamide molding materials having amino end groups excess as an adhesive protective layer of optical waveguides are described in DE 10 2004 045 775 A1. These polyamide molding materials are stabilized and preferably contain flame retardants.
Previous sheaths made of polyamide materials according to the prior art could not meet certain requirements optimally or could not meet them simultaneously. Thus, certain materials do not have a flame retardant or a halogen-free flame retardant, as is required above all for interior uses. For installations in the interior area and in automobile construction, the optical cores must additionally be able to bend well without buckling. For the use in the outside area (outside applications), robust sheaths are required, which protect the optical waveguides from weather influences and from gnawing by rodents. The collective term “rodents” not only means rodents according to the biological order here, but rather gnawing or biting animals of any type, e.g., rats, lagomorphs, or martens, which are among the predators.